Philip Johnston has been with the Daily Telegraph for more than 20 years. He is currently assistant editor and leader writer and was previously home affairs editor and chief political correspondent.

How honest will Alistair Darling be?

A layman's guide to the Pre-Budget ReportThe Government has promised to be as open and honest with the British people about the difficulties that lie ahead and the implications of today's pre-Budget report in the House of Commons. But how honest depends on whether the true meaning of the words used by Alistair Darling are fully understood. Here are some of the things he may say and what they mean.

Tell us the truth, Darling

'Pre-Budget report'. Once upon a time this was called the Autumn Statement. It is meant to be concerned solely with spending. If it is going to have tax elements in it, then it is really a mini-budget. But governments do not like talking about mini-budgets because they are a reminder of the dark days of the 1970s Labour government when they were a routine feature of the political landscape.

'National debt is low as a proportion of GDP'. It depends on what you include in the figures. The Government's own measurement puts it around 40 per cent of GDP. If Northern Rock is included it rises to 43 per cent. However, if you add in PFI charges for government spending that has been kept off the books, public sector pension commitments – and even the state pension, since there is no 'fund' on which to draw for those – then debt risies above 100 per cent of GDP.

'We are better placed than other leading industrialised nations to weather the downturn.' Mr Darling used this phrase in his Budget speech in March and will probably avoid repeating it for fear of being laughed out of the Commons. The Tories say we are, in fact, worse off than many other countries because no money from the surpluses of the boom years was put aside to allow for tax cuts or extra spending now without borrowing. This means the budget deficit – the difference between money raised from tax revenues and the sums spent – is already double the forecast made in the Budget. With today's announcements, it is likely to rise above Â£100bn within two years – greater than at any time since the 1970s.

Fiscal stimulus. This means borrowing more and deferring taxation.

America. Certain to be mentioned early on as the source of all our economic woes, as in 'This is a problem that started in America."

Worldwide crisis. See above.

Surprises. Will there be any? There used to be something called budget 'purdah', behind which the Chancellor would hide for weeks before his announcements and Government officials and ministers would observe this scrupulously. It had started to slip before Labour took office in 1997 but since then there has been no compunction on the part of the government to leak the entire contents of Budgets or other financial packages. That used to be unheard of. In the past, purdah was taken extremely seriously. Officials and advisers who took part in drawing up the Budget had to register each conversation with an outsider, particularly a journalist. Talking too much could, and did, cost a Chancellor his career. In 1947, the Labour Chancellor, Hugh Dalton, tipped off a Lobby correspondent to an increase in beer duty forgetting that he worked for an evening newspaper and the story was on the street before the Budget was delivered. Dalton resigned. Another alleged Budget leak came from Jimmy Thomas, a cabinet minister in the Baldwin government of 1936. He was playing golf with a City contact who took an ostentatious "Tee up" to mean an increase in tea duty. The financier took the hint and insured himself at Lloyd's against an increase in the tax on tea. He collected. Thomas paid the price by resigning. The main elements of Mr Darling's package have already been trailed in order to 'manage expectations'. But Mr Brown, in particular, likes to pull a rabbit out of the hat so there may yet be something unespected.

Smoke and Mirrors. These are what Mr Brown liked to deploy in his 11 Budgets as Chancellor. Often the devil was in the detail – and that was not discovered for hours or days later. This time we are promised honesty and transparency. We shall see.